JavaInvalid getInt（）的值無效

Question

我嘗試爲bukkit創建一個腳本。如果殺死一個殭屍，它需要在mysql表中增加1。怎麼了？或者有另一種方法？

錯誤：java.sql.SQLException中：爲getInt值無效（） - 'CraftZombie'

 PreparedStatement kills = connection.prepareStatement("SELECT ? FROM `data` WHERE name=?"); 
     kills.setString(1,entity.toString()); 
     kills.setString(2,name); 
     ResultSet result = kills.executeQuery(); 


     String entity_string = entity.toString(); 

     result.next(); 
     //int score = 1; 
     //score = result.getInt(1); 
     //Integer score2 = (Integer) result.getObject(entity_string); 

     int SC = result.getInt(entity_string); 



     PreparedStatement stat = connection.prepareStatement("UPDATE data SET ?=? WHERE name=?", 
       ResultSet.TYPE_FORWARD_ONLY, 
       ResultSet.CONCUR_UPDATABLE); 
     stat.setString(1,entity.toString()); 
     stat.setInt(2, SC + 1); 
     stat.setString(3,name); 

Answer 1

首先，不要做MySQL查詢事件，使服務器的滯後。

您必須創建包含要鏈接到mysql服務器的數據的hashmap，並執行查詢的調度程序異步任務。

實施例：

package test; 

import java.sql.DriverManager; 
import java.sql.SQLException; 
import java.util.Map.Entry; 
import java.util.UUID; 
import java.util.concurrent.ConcurrentHashMap; 

import org.bukkit.entity.Player; 
import org.bukkit.entity.Zombie; 
import org.bukkit.event.EventHandler; 
import org.bukkit.event.Listener; 
import org.bukkit.event.entity.EntityDeathEvent; 
import org.bukkit.plugin.java.JavaPlugin; 
import org.bukkit.scheduler.BukkitRunnable; 

import com.mysql.jdbc.Connection; 

public class Event extends JavaPlugin implements Listener { 

    // Mysql update data 
    public static ConcurrentHashMap<UUID, Integer> player_zombiekills = new ConcurrentHashMap<UUID, Integer>(); 

    // Mysql connection data 
    public static Connection connection; 
    private String host = "localhost"; 
    private String database = "DB"; 
    private String username = "user"; 
    private String password = "123"; 
    private int port = 3306; 

    //Kill zombie event 
    @EventHandler 
    public void zombieDeath(EntityDeathEvent eve) { 
     if (!(eve.getEntity() instanceof Zombie)) return; // Stop if death is not zombie 
     if (!(eve.getEntity().getKiller() instanceof Player)) return; // Stop if killer is not player 
     UUID uid = eve.getEntity().getKiller().getUniqueId(); // Save player uuid 
     if (player_zombiekills.contains(uid)) player_zombiekills.put(uid, 0); // Set kills 0 if not exist in hashmap 
     player_zombiekills.put(uid, player_zombiekills.get(uid) + 1); // plus 1 kills value 
    } 

    //On enable connection 
    public void onEnable() { 
     try { 
      if (connection != null && !connection.isClosed()) return; 
      Class.forName("com.mysql.jdbc.Driver"); 
      connection = (Connection) DriverManager.getConnection("jdbc:mysql://" + host + ":" + port + "/" + database, username, password); 
      if (!connection.isClosed()) System.out.println("[MySQL] " + "Connected to '" + database + "'"); 
     } catch (Exception e) { 
      System.err.println("[MySQL] " + e.getMessage()); 
     } 

     new BukkitRunnable() { 
      public void run() { 
       // for updates 
       for (Entry<UUID, Integer> ent : player_zombiekills.entrySet()) { 
        try { 
         // send update 
         connection.createStatement().executeUpdate("UPDATE `tablename` SET `zombiekills`=`zombiekills`+" + ent.getValue() + " WHERE `uuid`='" + ent.getKey().toString() + "'"); 
         // Sucess remove entry from hashmap to reset kills 
         player_zombiekills.remove(ent.getKey()); 
        } catch (SQLException e) { // If error 
         System.err.println("[MySQL] " + e.getMessage()); // Print error in console 
        } 
       } 
      } 
     }.runTaskTimerAsynchronously(this, 20, 20 * 60 * 10); // Run async loop every 10 minutes 
    } 
}